Circuit-protective device.



PATENTED NOV. 6, 1906.

D. G. JACKSON. CIRCUIT PROTECTIVE DEVICE.

APPLIUATION FILED SEPT. 24, 1904.

EVE- ur' Ilggald B.Jauksnn WiInessas:

useful Imfprovement in Circuit-Protective rrnirnn sra'r ns' err-ice i DUGALD (LJACKS'ON, or Maniacs, Wisconsin. cieouireorse'riss assess.

Specification of Emitters Patent;

racemes new, e, was.

Application filed September 19M. iisrlal g'ifiiigith.

To all whom it may concern:

Be it known that I, DUGALD O. Jncnson, a citizen ofthe United States, residing at Madison, in the county of Dane and State of Wisconsin, have invented a certain new and Devices, which the following is a full, clear,

' concise, and exact description, reference being had to the accompanying drawings, forming a part of this specification.

My invention relates to circuit-protecting apparatus; and it com rises a device for inc usion in an electric circuit to be rotected which will after an interval intro uce a resistance in the circuit to prevent destructive current-flow, but which does not interferewith the normal performance of the functions fort to free the drill-point.

cause burn-outs or other destructive results.

of the apparatus in the circuit. v

An occasion often arises in which it is desirable to reduce the current in a circuit after the current has been flowing for a-short time, particularly in such circuits as those wherein the apparatus operated'is desi ed to be included only momentarily, an a continued flow of current therethrough would soon Also whenmachinery driven by motorsis suddenly blocked or prevented from working, so that the motor is stalled, as by an excessive load, it' is sometimes desirable to maintain current flowing throu 'h the drivin -motor to assist in releasing tihe machine. With the usual protective devices the over load would result in the motor being discon-i nected from the circuit by the blowing offuses or o ening of circuit-breakers. My device, on t e other hand,,maintains the circuit at its working efficiency, While it at the same time protects the apparatus from injury ,due

to the abnormal currents which would flow under such circumstances if suitable protec tion was not afforded,

To illustrate'the operation of m device, I,

will refer to niotor-drivenrock-dr' ls.. When a drill becomes jammed, it is not desirable for the motor to be out from the circuit even thou h it isstalled by the overload; but it shouii continue toexert itstorque in an ef- My device included in circuit with such {a -machine will,

upon the occurrence of an excessive currentflow, due to the motor becoming overloaded or stalled, automatically introduce a resistance' into the circuit which-prevents a de structivc current-flow, While it maintains the torque of the motor. Many other situations may also arise where it is desirable to reduce the current in the circuit after an interval of time, and my-device is suitabie for such situations. r For the p ose of performing the functions aforesaid l'use an electromagnet which may be in the form. of, a solenoidwith a may-5- able core, the solenoid-windings being inclnded(either directiyor by means of a suit able shunt) in the circuit to heeontrolled; The core-or armature is arrangedei io act upon resistance may e introduced into the circuit ganjinterval of time clapses before'theresisb ture, and thearmature may be connected with the switch through a slotted ,With this arrangement thesolenoid-core rises slowl u on excessivelcurrent-flow tiiro h r the circuit, andafter an interval-of delay t e switch is actuated: 1 It desirabie for the motion of the" switch to be rap'd and this pass in the dash pctmechanism, so that at ,moved and the switch quickly opened to flow. of an excessive. current has been 1:81

its normal an safe condition the armature .tained intact, and the current will be of snfiioperation oi the apparatus.

which, upon excessive current-flow, are ordi narily actuated tocpen the working circuit 7 or incther ways to destroy its normal aficie'nc", which isundeslrable in the situations to w i h'mvinventidnnarticularly applies.

a switch, thro h the intervention ot which introduceresistance into the circuit. The; solenoid mechanism wiil' remain energized sufficiently to hold the resistance in circuit; until the cause producinga tendency to the moved; but ugonthe circuit again assuming;

iabout the time'the movement gf the switchbegins the opposition of the dash-pot is re-,

will be released and the switch again closed to, exclude the resistance from circuit.

'the resistance is in circuit, destructive m rentfiow through the apparatus in the cir-' uit is prevented; out the circuit is main cient strength to insure eficient and normal.

These imnor-" ,tant' features distniguish my device fromother protective devices heretofore employed 5 ,may be brought aboutby providing a hyp view of a formof my device, showing its con struction. 2 shows an application thereof for protecting apparatus. included in a si naling system, and Fig. 3 shows another apv ication; thereof for protecting a motor.

ilre reference characters r'efen to like parts throughout the various figures.

A solenoid-winding l is adapted to receive a core 2, a magnetic shroud 3' inclosing the windin and oflering'a ma etic path for the lines, o force created by ti: winding. This is; a desirable form for the electromagnet but its particular form is not essential to the invention. Dash-pot mechanism 4: may be mounted at the top of the solenoidcasing= and consists of a dash-pot cylinder 5, in which the plunger 6 is adapted tov reciprocats, the plunger being connected with the up er end of the solenoid-core by means of a re 7. ()penings 8 and 9 through the piston t; are covered by a dish-valve 10, which is loosely held in position by a headed pin. 11. An adjustable valve 12 is mounted over an opening 131 in the disk-valve registering with the opening 9. through the piston, and by adjustingthe size of the open ng 13* the amount of retardation upon, upward; stroke of the piston ma be adjusted. Upon downward stroke 0 the piston the disk-valve is released from the openings through the piston, allowing free passage of airtherethrough and quick return oi the piston. A link l4, connects with the lower end of the solenoid-core, and at its other end is provided with a slot 15, engaging a pin 16, secured near one end of the switch-blade 17, which switch-blade when closed serves to connect circuit-terminals l8 and k9, hetween which resistance 29- is bridged. The solenoid-winding 1 is referably connected serially in the circuit to be protected, while the switch -blade and resistance are normally connected in multiple series therein. Upon suflicient current-flow through the solenoid-windingthe core 2; will be attracted upwardly, and the switch-blade 1? will not move until the lower end of the slot 15 engages the pin 16. Owing to the dash-pot connection with the core 2, this u ward motion will be retarded, and about t e time that the pin l6 engages the lower end of the slot l5 means are rovi'd ed for removin the retardation and a lowing the attraction of the core to, cause the switch to. he quickly withdrawn from the terminal 19. This means may consist in a bypass 21, so ad assess justed as to allow immediate escape of the air above the piston in the dash-pot when the pin 16 is reached 0 the end of the slot 15. Upon the opening oi the switch the resistance 20 is included in the circuit and the excessive current reduced to a safe value. The core when in its up er position may come into contact or nearly into contact with an iron cap or fixed portion 01 core 22, which covers the upper part of the shroud 3 and extends a distance into the solenoid-core opening.

On account 01 the introduction of the resistance 20 into the circuit reduced current flowwill necessarily result through the winding- 1 but bymeans of the increased strength of attraction, due to the cap 22, the current strength through the solenoid-winding, although decreased, will still be sullicient to maintain the attraction of the core, and con sequently to maintain the resistance in circult during the time that an excessive cur rent tends to flow through the main circuit. Upon the current approaching its normal flow, however, the strength of attraction of the solenoid will he reduced and the core released, and, due to the weight of the core, which is not impeded by the dash-pot upon downward travel, the switch will be quickly closed and the resistance cut from circuit. The magnet-windingis in the main circuit, and is, therefore energized whenever current flows therethrough; but the core is adjusted by means of its weight or the effect of a spring, so that it is not lifted until the current becomes abnormal.

In Fig. 2 I have illustrated my invention applied to an arrangement of block-signals which has been used in connection with elec tric railways forthe purpose of indicating to the crew of a car at a siding whether or not a car already occupies the single track which leads to the next siding ahead. At each siding or turnout in the single track contactstrips 23 24: and 23 24, respectively, are provided, these contact-strips hein associated with the trolleywire 25. Upon the passage of atrolley-wheel under a contact-strip the strip is briefly connected with the trolley-wire. A car passing under the contact-strip 23* causes momentary connection therewith with the trolley-wire 25, and current momentarily flowsffrom the trolley-wire through the conductor 26, switch 27,: and divides, part flowing through the electroma net 28 through the conductor 29 to, groun the remainder flowing through the conductor 30, electromagnet 31 at the succeeding siding, and through conductor; 29 to ground. The switch 32 will thus be closed u on attraction of the pivoted switch-lever 33 y the magnet 31, and a circuit will be closed from the trol- Icy-wire 25, through conductor 34, through lamps or resistance 36, through the signallamps 36. 36., the current here dividing, part passing through electromagnet 31- and IIO . through conductor 29 ing current passingthrough conductor and ""tromagnet through electromagnet 28 to ground. Elec- 28 upon energization attracts the armature 37 to close a switch 37 between conductor 38 and signal-lamps 39 39 to ground. Any other car now a proaching either siding will see the burning ights 36 36 or 39 39 and will know that a car occupies the track. When the car has traversed the track from contact-stri 23 to contact-strip 24, thus traversing t e block, its trolley touches the'contact-stri '24 and a niomentary current-flow is esta conductor 40 and through the electroma net 41 to ground through conductor 29. he sWi'tch-arm-33' is now' attracted by magnet 41 to close the switch 27 and to open the switch 32'. Opening the switch 32, however, breaks the circuit through the signallamps 36 and through the electromagnet 28 thus extinguishing t e signal-lamps and indicatin to the cars approaching the single track that the track is clear in the block. A single track in the reverse clears the signals by the car passing on the direction sets and contact-strips-ZS' and 24. The electromagnets for controlling the switches in a circuit of this kind are usually intended-for only; I momentary energizationyand continued curi p 29, for instance, or in any other, appropriate part of the circuit. Upon continued currentflow with the protecting device in circuit the cores thereof will be gradually attracted, and if the current-flow be continued long enough the cores will eventually openthe respective switches 17 17, controlled thereby, and thus introduce a resistance in circuit which prevents the current-flow from becomingof injurious strength, and thus prevents injury to the electromagnets.

In Fig. 3 I have. shown another application of the controlling apparatus. 1 have shown a rock-drill 42 operated by an electric motor 43, and in the circuit for this motor I include the protecting device. Drills of this kind very often become 'jammedin rock, for in stance, and it is desirable that the motor torque be maintained on the drill to assist in its release. The motor, however, being unable to rotate, is traversed by an excessive current flowing through its Windin s unless protective means areprovided. int c applito ground, the

lished through the" and if the motor becomes stalled or an ex-- cessive currentflows for any cause the resistsince 20 is introduced in circuit and thecurrent through the nictor is limited to a safe value; Atthe same time the circuit is mainertits tor u of the'drill the current may assume its normalflow) and the solenoid will release its armature and the resistance is again shunted from the circuit.

Y My "invention is thus a improvement. over protective devices heretofore used. It does not open or in. anywaydestroythe devices from becoming injured from exces- "dition. My invention also continues to act in protecting the circuit until the cause of theexcessive current is withdrawn, and if the while the protective device remains ready to when conditions require it described are only exarnp es oi numerous in;

sincethe adaptation of my invention to other appropriate situations will now heunderstood. f 1 claim as new and v desire to secure hy Lettors Patent-e circuitnorma ly short-circuited by a switchcircuit, an armature adapted to be attracted within said winding upon energization thereof, a slotted link connecting said armature with sald switchkblade for reventing moveof movement of. the core u on attraction thereon, and means for retar ing the move ment of sald core during sald interval, said switch-blade to be en aged to be moved upon short-circuit about said resistance, said resistance being effectively included in circuit Withoutfinterfering with the normal operation of the translating devices in said circuit.

2. The combination with a circuit containing translatin devices, of a resistance in said circuit norma ly ShOI't-Cll'fillltQd by a switchin said circuit anarmature-core adapted to be attractedwithin said winding upon enere tainedintact and the motor continues to ex-' e on the Upon the release effectiveness or eiiiciency of the working cir-r cuit; but it 'servesto prevent the Operative sive current, while these devicesare at the same time maintained'in their operative concurrentagain falls toits normal-value the circuit is restored. ,to -its original condition,

perform its protedtive functions over again Thesignal-circuits and motor-circuits connection with which in invention is'here.

I 1.: The conibinationwith a circuit contain 111g translatin devices, of a resistance in said blade, 'af solenoid-winding included in said slotted link after said interval causing saidfurther attraction o I said core to open the -cation ofrmyinventi'onthe solenoid of the protecting device is included in the circuit,

stances in which it can he successfully and advantageously emploged, and I do not wish to-be limited to these. escrihed applications,-

nientoi said switch-blade uring an intervalblade, s solen id-vdnding included serially,

gization. thereof, a slotted link connecting said armature with said Switchblade: for re venting actuation of said switch-blade ur ing an interval, saidslotted link after said interval allowing said switch-blade to be moved by said attracted core to open the short circuit about said resistance, said resistance being thereupon included serially in said circuit.

3. The combination with a circuit including translatin devices, of a resistance in said circuit norms y short-circuited by a switchblade, a solenoid-winding included serially in said circuit, an armature-coreadapted to be attracted within said winding upon energizetion thereof, a slotted link connecting said, armature-core with said switch-blade to prevent actuation of said switch-blade for a certain distance of attraction of said core within said winding, means for retarding the motion of said core during said distance, said-link upon further attraction beyond said distance causing said switch-blade to be -moved to open said short circuit about said resistance, and means for removing the retail-din influence after a predetermined intervzfi whereby said switch-blade is quickly act-u ated.

e. The combination with acircuit containing translating devices, of a resistance in said circuit normally short-circuited by switchblade, a solenoidwinding included in said circuit, an armature-core adapted to be attracted within said winding upon energizetion thereof, said armature being connected with said switch-blade by means of a slotted link so arranged that the switch-blade will not be effectively engaged until the armature-core has almost com leted its movement, means for retarding t e motion of said armature during'said movement thereof, and means for releasing the retarding means from the'armature near the end of its movement to allow the armature 'to quickly finish its movement and to quickly move the switch blade to remove its -shortcircuiting efi'ect from the resistance.

5. The combination with a circuit-containing translating devices, of a resistance in said assess circuit normally short-circuited by a switchblade, a solenoid-winding included in said circuit, an armature-core adapted to be attracted within said winding 11 on energization thereof, a connecting-1m connecting said armature with the switch-blade, means for causing relative movement between the connectinglink and switch-blade during movement of the armature to almost finish its stroke, dash-pot mechanism connected with the armature and adjusted to retard its movement during relative movement be tween the connecting-link and the switchblade, and means for destroying the retard- :ing ellect of the dash t mechanism during the end of the stroke 0 the armature to allow quick movement of the armature and quick movement of the switch-blade to remove its "shortcircuiting effect from the resistance.

6. The combination with a circuit including translating devices, of a resistance in' said circuit, short-circuiting means for normally rendering said resistance ineffective, a solenoid-winding included in said circuit, an armature-core adapted to be attracted within said winding on excess current-flow through the circuit, connecting means between the armaturecore and the short-circuiting means said connecting means being inefl'ective during the beginnin of the armature movement, dash-pot me ianism for retarding the initial movement of the armature core and means for destroying the retarding effect of the dash-pot mechanism near-the end of the armature movement to allow said armature to quickly finish its movement, and means for causing the connecting means to become etle'ctive during this quick move ment period of the armature-core whereby the short-circuiting means is quickly actuated to allow the resistance to become effective.

' lln witness whereof I hereunto subscribe my name this 20th day of September, A. D. 1904:.

DUGALD C. JACKSON.

Witnesses CriARLEs J. SCHMIDT, LEONARD W. NOVANDER. 

